The introduction of Methanesulfonato{[4-(N,N-Dimethylamino)Phenyl]Di-T-Butylphosphino}(2'-Amino-1,1'-Biphenyl-2-Yl)Palladium(II)

General description

The Methanesulfonato{[4-(N,N-Dimethylamino)Phenyl]Di-T-Butylphosphino}(2'-Amino-1,1'-Biphenyl-2-Yl)Palladium(II), with the CAS No: 1820817-64-8, is also known as Amphos Palladacycle Gen. 3. This chemical’s molecular formula is C29H41N2O3PPdS and molecular weight is 635.11. Its melting point is 192-201 °C (decomposition) and it is a beige to tan powder. It is a kind of mental catalyst. Its structure is as follows:

Figure 1 Appearance of Methanesulfonato{[4-(N,N-Dimethylamino)Phenyl]Di-T-Butylphosphino}(2'-Amino-1,1'-Biphenyl-2-Yl)Palladium(II).

Chemical synthesis of Methanesulfonato{[4-(N,N-Dimethylamino)Phenyl]Di-T-Butylphosphino}(2'-Amino-1,1'-Biphenyl-2-Yl)Palladium(II)

Methanesulfonato{[4-(N,N-Dimethylamino)Phenyl]Di-T-Butylphosphino}(2'-Amino-1,1'-Biphenyl-2-Yl)Palladium(II) can be synthesized by single step according to the previous work [1]. Amphos Pd G3 was synthesized with reference to the synthesis of other G3 complexes such as SPhos Pd G3 and XPhos Pd G3. [2] μ-OMs dimer (763 mg, 1.03 mmol), which was prepared by the reported procedure [2], and 4-(di-tert-butylphos- phino)-N,N-dimethylaniline (Amphos; 548 mg, 2.06 mmol) were placed in a 25 mL Schlenk tube. After evacuation and backfilling with argon, THF (15 mL) was added. The resulting dark brown solution was stirred at room temperature for 30 min. About 90% of the solvent was concentrated in vacuo, and then, the residue was triturated with pentane to give Amphos Pd G3 as a pale-yellow solid. Yield 1.05 g (1.65 mmol, 80%). ¹H NMR (500 MHz, CDCl₃): δ 1.13 (d, J = 14.0 Hz, 9H), 1.29 (d, J = 13.8 Hz, 9H), 2.74 (s, 3H), 2.97 (s, 6H), 4.72 (br, 1H), 6.53 (d, J = 7.7 Hz, 2H), 6.60 (td, J = 7.6, 0.9 Hz, 1H), 6.81 (dd, J = 8.0, 4.0 Hz, 1H), 6.92 (t, J = 7.3 Hz, 1H), 7.17?7.21 (m, 2H), 7.27 (td, J = 7.5, 1.3 Hz, 1H), 7.41 (br t, J = 8.6 Hz, 2H), 7.45? 7.49 (m, 2H), 7.53 (br d, J = 6.3 Hz, 1H); ³¹P{1H} NMR (200 MHz, CDCl₃): δ 64.

Figure 2 Chemical synthesis of Methanesulfonato{[4-(N,N-Dimethylamino)Phenyl]Di-T-Butylphosphino}(2'-Amino-1,1'-Biphenyl-2-Yl)Palladium(II).

Application of Methanesulfonato{[4-(N,N-Dimethylamino)Phenyl]Di-T-Butylphosphino}(2'-Amino-1,1'-Biphenyl-2-Yl)Palladium(II)

Methanesulfonato{[4-(N,N-Dimethylamino)Phenyl]Di-T-Butylphosphino}(2'-Amino-1,1'-Biphenyl-2-Yl)Palladium(II) is a kind of Palladium catalyst. Palladium-mediated cross-coupling reactions to form C?C, C?N, C?O, and C?S bonds (e.g., Buchwald?Hartwig aminations) are among the most powerful organometallic transformations employed in organic synthesis [3]. Over the past thirty years palladium-catalyzed coupling reactions have become powerful tools for generating carbon–carbon and carbon–heteroatom bonds [2]. The catalytic reaction cycle typically involves three steps: (i) oxidative addition of Pd0 with aryl halide, (ii) formation of palladium(II) complex through transmetalation, and (iii) regeneration of the active Pd0 catalyst through reductive elimination. Pd(II) sources, such as Methanesulfonato{[4-(N,N-Dimethylamino)Phenyl]Di-T-Butylphosphino}(2'-Amino-1,1'-Biphenyl-2-Yl)Palladium(II) must be reduced in situ.

Mass spectrometric pattern of Methanesulfonato{[4-(N,N-Dimethylamino)Phenyl]Di-T-Butylphosphino}(2'-Amino-1,1'-Biphenyl-2-Yl)Palladium(II)

The Methanesulfonato{[4-(N,N-Dimethylamino)Phenyl]Di-T-Butylphosphino}(2'-Amino-1,1'-Biphenyl-2-Yl)Palladium(II) intermediates can be detected by desorption electrospray ionization according to the previous work [3]. Upon mixing Methanesulfonato{[4-(N,N-Dimethylamino)Phenyl]Di-T-Butylphosphino}(2'-Amino-1,1'-Biphenyl-2-Yl)Palladium(II) in THF, a major ion corresponding to the cation of it at m/z 539 appeared in the acquired desorption electrospray ionization spectrum (DESI-MS). Figure 3 shows that once NaOtBu in MeOH was introduced and online mixed with Methanesulfonato{[4-(N,N-Dimethylamino)Phenyl]Di-T-Butylphosphino}(2'-Amino-1,1'-Biphenyl-2-Yl)Palladium(II), the sodium-adducted Pd⁰L species at m/z 394 was formed and immediately captured by MS. It is reasonable that sodiated Pd0L rather than the protonated Pd⁰L was detected because the reaction mixture has excess NaO^tBu. The inset in Figure 3 clearly shows the zoomed-in spectrum of [Pd⁰L + Na]+ at m/z 394, which exactly matches its theoretical isotopic peak distribution. With the ability to detect the catalytically reactive Pd⁰L species using the DESI-MS approach, the ability to detect other species is investigated within the reaction cycle. Premixing Methanesulfonato{[4-(N,N-Dimethylamino)Phenyl]Di-T-Butylphosphino}(2'-Amino-1,1'-Biphenyl-2-Yl)Palladium(II) with iodobenzene (PhI), and further mixing with NaOtBu, allowed the in situ generated Pd⁰L species to undergo oxidative addition with PhI to produce [LPdPh]⁺, which was successfully observed at m/z 448. Besides the observation of Pd⁰L (m/z 394) and [LPdPh]⁺ (m/z 448), generation of a new set of peaks at m/z 647 indicated the successful formation and detection of the PdII-amine complex, [LPd^IIPh(HN₂R)]⁺.

References

[1]Masuda et al. Late-Stage Functionalization of the Periphery of Oligophenylene Dendrimers with Various Arene Units via Fourfold C-H Borylation. Journal of Organic Chemistry, 2021, 86(21): 14433-14443.

[2]Bruno et al. Design and preparation of new palladium precatalysts for C-C and C-N cross- coupling reactions. Chem. Sci. 2013, 4, 916?920.

[3]Zheng et al. Capture of Reactive Monophosphine-Ligated Palladium(0) Intermediates by Mass Spectrometry. Journal of the American Chemical Society, 2015, 137(44): 14035-14038.

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